Some manufacturers produce semiconductor wafers at one geographical location and have the wafers further processed at another geographical location. Also, some manufacturers ship large quantities of packaged wafers to other geographical locations. In such cases, the wafers are often delivered in a container filled with wafers in a horizontally stacked configuration. Such containers are sometimes referred to as coin stack boxes.
Many wafers have interconnection conductor material portions (e.g., solder bumps, bond pads, post-passivation interconnects) protruding from the wafer surface. There have been problems with the interconnection conductor material portions being damaged when shipped in coin stack boxes in a horizontally stacked configuration. The damage often occurs when the surface of one wafer is in contact with the back side of a wafer above it. Currently, a 2-3 mil thick sheet of antistatic film is placed between stacked wafers. But even with a wafer separator sheet between the wafers, the damage often still occurs. Scratches may occur on wafer surfaces due to particles or contamination on the antistatic film. During shipping, the interconnection conductor material portions may experience sheer forces (e.g., from one wafer rotating and/or shifting relative to another wafer). Such sheer forces tend to smear and/or shear some of the interconnection conductor material portions. Also, the interconnection conductor material portions are often flattened during shipping. Because the interconnection conductor material portions are often grouped very close together, such smearing and/or flattening may cause adjacent interconnection conductor material portions to be electrically connected, which is highly undesirable. Also, a sheared interconnection conductor material portion often acts as a disconnect or a resistor that will quickly burn through during normal current flows, which is also highly undesirable. Hence, there is a need for a way to ship horizontally stacked wafers while not damaging the interconnection conductor material portions extending from the wafers.
An experiment has shown that shipping wafers in a vertically position using existing vender boxes results in little or no damage to the interconnection conductor material portions extending from wafers. However, shipping the wafers in a vertically stacked and separated configuration can be more expensive than shipping them in a horizontally stacked configuration, as it may require a larger volume of space when shipping. Also, some manufacturers already have large investments in wafer carrier containers adapted for containing horizontally stacked wafers therein. Thus, it would be highly desirable to enable a way to use the existing wafer carrier containers for horizontal stacking, while preventing damage to the interconnection conductor material portions extending from the wafers during shipping.